In “Smashed,” an alcoholic couple —Mary Elizabeth Winstead and Aaron Paul as Kate and Charlie Hannah — have their marriage tested when one of them decides to stop drinking. It’s a movie about alcoholism made by a director and starring actors who acknowledge knowing little about the subject.

“I don’t know that experiencing it was necessary,” director James Ponsoldt says. “The fact is everybody struggles with something potentially life-altering, at some point in their lives. And so it was on knowing people and exploring people and our sometimes surprisingly common problems.”

“Smashed,” which opens here on Friday, starts out with the couple in a neighborhood dive bar with Kate butchering a folk song on a karaoke machine, as a woozy Charlie grins goofily.

It is a sign of things to come that Kate, an elementary school teacher, decides to leave Charlie at the bar after her performance, because she has to work the following morning. Hung over, she vomits in front of her students and lies to her school principal, played by Megan Mullally, about why she’s sick.

As Kate grows increasingly disgusted with her own behavior, Charlie, a writer who works from home, becomes increasingly frustrated with her reluctance to share their favorite pastime. That tension peaks when Kate decides to quit drinking altogether,

“I grew up in a dry county in Utah,” Winstead (“Scott Pilgrim vs. the World”) says. “And my family was pretty strict, Southern Baptist. So I never experienced alcoholism firsthand. I mean, I drink now. My friends drink. But I’ve never been close to anyone who drank to excess. So preparing for this role and understanding Kate’s frame of mind and her struggle meant talking to people who have struggled with substance abuse and simply exercising my craft and thinking hard about how I work through my own issues, compared to Kate.”

Winstead says she did not watch other movies about substance abuse for fear she’d corrupt her own portrayal. But she knows there are plenty of films out there about excessive drinking — from “Leaving Las Vegas” to “Who’s Afraid of Virginia Woolf?” and “Days of Wine and Roses.” Another drinking film, “Off the Black,” starring Nick Nolte as a sad sack alcoholic baseball umpire estranged from his son, was, like “Smashed,” directed by Ponsoldt.

“The notion of this film is fascinating,” says Sarah Allen Benton, a mental health counselor and author of “Understanding the High-Functioning Alcoholic: Professional Views and Personal Insights.” “Often when I discuss HFA in speeches, I mention that media and the entertainment world have done a horrible job accurately portraying HFAs, because there is this tendency to either glamorize the addiction or downplay it as something fun-loving and under control. And the truth is a lot more boring.”

It’s boring, she says, because high-functioning alcoholics are everywhere. According to one study Benton wrote about by the International Journal of Law and Psychiatry, veteran attorneys with up to 20 years experience showed evidence of problem drinking at a rate of 18 percent — it rose to
25 percent for attorneys with more than 20 years experience.

Because high-functioning alcoholics are able to make it to work or school on time and perform well, they’re often given a pass by friends and colleagues, who may tend to stereotype alcoholics as being homeless, jobless, and poor.

Ponsoldt, who says he enjoys making films about “people with issues,” says he sees a common denominator in the struggles of addicts like Kate and Charlie and the emotional struggles of non-addicts.

“I did direct ‘Off the Black’,” he says, “but that was less about the disease and more about the relationships. But what I notice is that all of these struggles that involve our feelings for other people really show how human we are.”

The film he’s now working on, “The Spectacular Now,” which also stars Winstead, is about a popular high school kid who woos a social outcast as a joke, until he realizes that being her friend could be good for them both.

Winstead also stars in “A.C.O.D.,” a comedy set for release in 2013 about a man coping with the aftermath of his parents’ divorce 15 years after the fact, when he learns he was secretly filmed as a child for a study on children of divorce. That revelation and his participation in a follow-up documentary traumatizes the man’s new family.

“I don’t have a dream role or a dream type of role,” she says, joking for a moment that “Smashed” is the third consecutive film in which her character is named Kate. “That’s as close as I want to come to typecasting. But I acknowledge this role will probably open doors for me. And really what I want most from that is the ability to keep working with directors like James, and the ability to pick roles just because I love the character and the script and not because I need the role to raise my profile or for a paycheck.”

She does, however, vow to keep seeking roles that help her “better understand myself and how I relate to the people in my life.”